Power companies may be hiding their profits from energy regulator Ofgem and understating how much they make from consumers, a senior MP warned this weekend.

Shadow Energy Secretary Caroline Flint has written to Tim Yeo, chairman of the Energy and Climate Change Committee, to warn that accounting methods could be obscuring how much energy groups earn from UK households, making it harder for Ofgem to regulate pricing.

The concerns raised in a letter seen by The Mail on Sunday follow the revelation last week that many of the big six energy firms – RWE npower, ScottishPower, SSE, Eon, Centrica and EDF – pay little or no tax in Britain.